Publications

Abstract Although a great variety of classical force fields (FFs) for room-temperature ionic liquids (RTTLs) have been recently suggested, no systematically derived non-polarizable model is able to reproduce their transport properties, i.e. diffusion constants, conductivities and viscosities. In the present paper, we show that modern FFs greatly overestimate pairwise electrostatic interaction energies in the RTILs systems leading to extremely hindered ionic motions. Based on the results of our ab initio molecular dynamics calculations using explicit ionic environment, we modified the electrostatic interaction potential of 1-ethyl-3-methylimidazolium tetrafluoroborate. Starting from FF, originally derived by Liu et al., we further refined it, so that it reproduces experimental transport properties without compromizing either structure or thermodynamics. The main advantages of the suggested phenomenological account for electronic polarization are its consistency, clearness, simplicity and the possibility to improve functionality of the existing FFs by modifying exclusively atomic partial electrostatic charges. ©The Electrochemical Society.

Abstract The action of sinapic acid and its alkyl esters as potential antioxidants has been investigated. For this purpose, a series of sinapic acid ester derivatives was synthesized and their antioxidant activities were evaluated using distinctive analytical methods, namely, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and FRAP UV-vis methods and differential scanning calorimetry. The electron-donating activity and lipophilicity of these phenolic compounds were also evaluated. From the overall results it was concluded that alkyl ester sinapates (linear alkyl esters) present almost the same antioxidant activity, albeit slightly lower, exhibited by the parent compound (sinapic acid). Furthermore, the addition of an alkyl ester side chain has a positive effect on the partition coefficient of sinapic acid, improving its utility as an antioxidant in a more lipophilic medium. The data on the antioxidant activity obtained by different analytical methods correlated well with each other and have revealed interesting antioxidant data of alkyl esters of sinapic acid.

Abstract Chromone carboxylic acids were evaluated as human monoamine oxidase A and B (hMAO-A and hMAO-B) inhibitors. The biological data indicated that only chromone-3-carboxylic acid is a potent hMAO-B inhibitor, with a high degree of selectivity for hMAO-B compared to hMAO-A. Conversely the chromone-2-carboxylic acid resulted almost inactive against both MAO isoforms. Docking experiments were performed to elucidate the reasons of the different MAO IC(50) data and to explain the absence of activity versus selectivity, respectively.

Abstract In recent years flavonoids have attracted a great interest as potential therapeutic drugs against a wide range of diseases. While the antioxidant activity of these natural polyphenolic compounds is well known, their binding to DNA characteristics is not fully understood despite the fact that many of them exert their biological effects by reversibly binding to nucleic acids. The present study aims to investigate the interaction of flavone and four hydroxyflavone isomers with double stranded DNA, occurring in bulk solution. A combination of micro-DSC and UV spectroscopy has been used to study the effect of these compounds and of their structure on the structure and stability of the DNA molecule. The characteristics of DNA thermal denaturation have been used as a measure of the effect of the compounds on the stability of the double helix. Micro-DSC has been used to determine the temperature dependence of the heat capacity of the process of thermal denaturation of DNA in solutions containing flavone and the following hydroxyflavones: 3-hydroxyflavone, 5-hydroxyflavone, 6-hydroxyflavone and 7-hydroxyflavone. The observed enthalpy of transition and the transition temperature of DNA thermal denaturation were determined for each compound. UV thermal denaturation curves were also recorded, under the same experimental conditions as the DSC measurements. The transition temperature values and the thermodynamic parameters of thermal denaturation were determined. Differential scanning calorimetry and ultraviolet spectroscopy measurements have evidenced an interaction between the studied flavones and DNA, showing a stabilization of DNA structure, due mainly to intercalation of the flavones. The results also show a noteworthy effect of the structure of the hydroxyflavone isomers on this stabilization.

Abstract A static method was used to measure the vapor pressures of crystalline and liquid phases of benzamide, N-methylbenzamide, and N,N-dimethylbenzamide, in the temperature ranges (344.8 to 438.2) K, (322.9 to 388.4) K, and (297.0 to 361.7) K, respectively. The vapor pressures of the crystalline phase of benzamide were also measured using the Knudsen effusion method in the temperature range (324.1 to 344.2) K. From the experimental results, the standard molar Gibbs energies and enthalpies of sublimation and of vaporization, at T = 298.15 K, and the triple points coordinates (p,T) for the three compounds were derived. The temperatures and molar enthalpies of fusion were also determined using differential scanning calorimetry and were compared with the values derived from the vapor pressure measurements. The results enabled the determination of the hydrogen bond enthalpies in the studied compounds.

Abstract A static method was used to measure the vapor pressures of crystalline and liquid phases of ortho-, meta-, and para-fluorobenzamides, in the temperature ranges (318.0 to 412.2) K, (336.8 to 432.0) K, and (344.8 to 437.8) K, respectively. The vapor pressures of the crystalline phase of the ortho- and meta-isomers were also measured using the Knudsen effusion method in the pressure ranges (0.1 to 1) Pa. From the experimental results, the standard molar Gibbs energies and enthalpies of sublimation and of vaporization, at T = 298.15 K, and the triple-point results (p, T) for the three compounds were derived. The temperatures and molar enthalpies of fusion were also determined using differential scanning calorimetry and were compared with the values derived from the vapor pressure measurements. The enthalpy of the intermolecular hydrogen bonds N-H center dot center dot center dot O in the studied compounds will be discussed and compared with the values derived for benzamide.

Abstract A new fluorescent sensor for nitric oxide (NO) is presented that is based on its reaction with a non fluorescent substance, reduced fluoresceinamine, producing the highly fluorescent fluoresceinamine. Using a portable homemade stabilized light source consisting of 450 nm LED and fiber optics to guide the light, the sensor responds linearly within seconds in the NO concentration range between about 10-750 mu M with a limit of detection (LOD) of about 1 mu M. The system generated precise intensity readings, with a relative standard deviation of less than 1%. The suitability of the sensor was assessed by monitoring the NO generated by either the nitrous acid decomposition reaction or from a NO-releasing compound. Using relatively high incubation times, the sensor also responds quantitatively to hydrogen peroxide and potassium superoxide, however, using transient signal measurements results in no interfering species.

Abstract The standard (p(0) = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of five aminomethoxybenzoic acids, at T = 298.15 K, were derived from the standard molar energies of combustion in oxygen, measured by static-bomb combustion calorimetry. Combining these results with literature results of the standard molar enthalpies of sublimation, at T = 298.15 K, the standard molar enthalpies of formation, in the gaseous phase, were derived. Additionally, the enthalpies of formation of the ten possible isomers of aminomethoxybenzoic acid were estimated using accurate Double Hybrid Density Functional Theory (DHDFT) computational methods. The good agreement between the experimental and estimated values of the enthalpies of formation of the five isomers studied experimentally allows us to be confident on the estimated values for the other five isomers. A quantitative evaluation and analysis of the aromatic character of all the studied isomers based on the calculation of Nucleus Independent Chemical Shifts (NICS) was also conducted.

Abstract Aberrantly regulated apoptosis is involved in the pathogenesis of several diseases and defective apoptosis leads to uncontrolled cell proliferation and tumorigenesis. Cancer is an example of a pathologic condition where the normal mechanisms of cell cycle regulation are dysfunctional either by excessive cell proliferation, inhibited/suppressed apoptosis or both. Dietary habits are estimated to contribute to, at least, one third of all human cancers, showing that dietary components can exacerbate or interfere with carcinogenesis. However, several epidemiological studies have revealed that some dietary factors can decrease the risk of different types of cancer. Apoptosis is suggested to be a crucial mechanism for the chemopreventive properties associated with several dietary factors by eliminating potentially deleterious (damaged/mutated) cells. Food, a readily available item, contains several promising chemopreventive agents. Polyphenols are serious candidates since they are responsible for the cancer protective properties of a diet rich in vegetables and fruits: numerous phenolic compounds showed antiproliferative and cytotoxic effects and, more specifically, pro-apoptotic activities, in several cancer cells lines and animal tumor models. The aim of the present review is to analyze and summarize several aspects related to the molecular mechanisms of apoptosis induced by dietary factors with particular emphasis on polyphenols. Dietary factors that can activate cell death signals and induce apoptosis, preferentially in precancerous or malignant cells, and the study of their apoptotic inducing targets can represent a mean to devise new strategies for cancer prevention in the future.